摘要:
Novel compositions of nucleotide analog prodrugs for the treatment of viral infections and cancer are herein disclosed. The prodrugs have a biocompatible polymeric carrier conjugated to the nucleotide analog via an amino-phosphate linkage. The amino group is provided by the carrier, which either inherently possesses a primary amine, or is modified with reactive groups that incorporate the primary amine onto the carrier. The carrier can be a polyamino acid, a polyvinylic polymer, a polysaccharide or combinations thereof, such as polylysine, HPMA, dextran, hydroxyethyl starch, or polyethylene glycol; the nucleotide analog can be ribavirin araA, AZT, acyclovir, 5-FUDR, araC or ddI. Methods of treating a viral infection of cancer using these prodrugs are also disclosed. The prodrugs endow the nucleotide analogs with substantially enhanced therapeutic efficacy and reduces toxicity in comparison to the nucleotide analog alone.
摘要:
This invention relates to materials exhibiting certain magnetic and biological properties which make them uniquely suitable for use as magnetic resonance imaging (MRI) agents to enhance MR images of animal organs and tissues. More particularly, the invention relates to the in vivo use of biologically degradable and metabolizable superparamagnetic metal oxides as MR contrast agents. Depending on their preparation, these metal oxides are in the form of superparamagnetic particle dispersoids or superparamagnetic fluids where the suspending medium is a physiologically-acceptable carrier, and may be uncoated or surrounded by a polymeric coating to which biological molecules can be attached. These materials are administered to animals, including humans, by a variety of routes and the metal oxides therein collect in specific target organs to be imaged; in the case of coated particles, the biological molecules can be chosen to target specific organs or tissues. The biodistribution of the metal oxides in target organs or tissues results in a more detailed image of such organs or tissues because the metal oxides, due to their superparamagnetic properties, exert profound effects on the hydrogen nuclei responsible for the MR image. In addition, the dispersoids and fluids are quite stable and, in the case of the fluids, can even be subjected to autoclaving without impairing their utility. Furthermore, the materials are biodegradable and, in the case of iron oxide compounds, can eventually be incorporated into the subject's hemoglobin, making them useful in treating anemia. Thus, the materials are well-suited for in vivo use.
摘要:
This invention relates to an improved method for obtaining the in vivo MNR image of an organ or tissue of an animal or human subject. More specifically, this invention relates to the use of small (about 10 to about 5,000 angstroms in diameter) biodegradable superparamagnetic metal oxide particles for use as imaging agents. The particles, which may be uncoated or surrounded by a stable polymeric coating, can be mixed with a physiologically acceptable medium to form a uniform dispersoid which can be administered to the subject by a variety of routes. Once administered, the particles collect in the target organ or tissue where they will remain for a time sufficiently long for an image to be obtained, but are ultimately metabolized or cleared within about 7 days.
摘要:
The preparation and isolation of biodegradable superparamagnetic MR imaging contrast agents for the vascular compartment is described. These aggregates are comprised of individual biodegradable superparamagnetic metal oxide crystals which aggregates have an overall mean diameter less than about 4000 angstroms. The preferred vascular imaging contrast agent is comprised of aggregates of iron oxide crystals having an overall mean diameter less than about 500 angstroms. These contrast agents may be associated with a macromolecular species, which assist, among other things, in the preparation of these extremely small materials, and may be dispersed or dissolved in a physiologically acceptable medium. Preferred media also stabilize the materials against further aggregation even under harsh sterilization conditions. The autoclaved biodegradable superparamagnetic iron oxides of the invention are ideally suited for a pharmaceutical preparation and enjoy several advantages over prior intravascular imaging contrast media including low osmolality, low effective dose requirements, high relaxivities, long blood lifetimes, rapid biodegradability, and versatility with respect to a wide range of applicable MR data acquisition parameters.
摘要:
A new ligand binding assay is based upon measurements of relaxation rates of the solvent, which are obtained with a magnetic resonance (MR) spectrometer. It is termed a solvent mediated relaxation assay system (SMRAS). SMRAS is based on the observation that the enhancement of proton relaxation rates produced by a magnetic material can be modulated by the binding of various analytes to a magnetic material. Hence the relaxation rate of the solvent can be interpreted to give information on the concentration of an analyte.
摘要:
This invention relates to a method of directing a therapeutic agent to selected cells, wherein a complex is formed between a polysaccharide capable of interacting with a cell receptor and a therapeutic agent. The resulting complex is administered to a subject, and permitted to be internalized into the selected cells through a process known as receptor mediated endocytosis (RME). The polysaccharide may be, for example, arabinogalactan, gum arabic, mannan or hydrolysis products thereof; the therapeutic agent may be, for example, an antiviral agent, a nucleic acid, hormone, steroid, antibody, chemoprotective or radioprotective agent. The cell receptor may be for example, the asialoglycoprotein receptor or the mannose receptor.
摘要:
A new class of magnetic resonance (MR) contrast agents are described whose in vivo biodistribution is based upon the ability of certain cells to recognize and internalize macromolecules, including the MR contrast agents of the present invention, via a process which substantially involves receptor mediated endocytosis. The RME-type MR contrast agents described herein comprised of biodegradable superparamagnetic metal oxides associated with a variety macromolecular species, including but not limited to, serum proteins, hormones, asialoglycoproteins, galactose-terminal species, polysaccharides, arabinogalactan, or conjugates these molecules with other polymeric substances such as a poly(organosilane) and dextran. One of the advantages or these MR contrast agents is that they may be selectively directed to those cells which bear receptors for a particular macromolecule or ligand and are capable of undergoing receptor mediated endocytosis. An MR contrast agent prepared from biodegradable superparamagnetic iron oxide and asialofetuin, or more preferably arabinogalactan, for example, is selectively localized in the hepatocytes the liver with no significant accumulation in the spleen. An MR experiment which can be carried out shortly after administration to the subject of the contrast agents of the invention can thus provide a method for obtaining an enhanced MR image, as well as valuable information regarding the functional or metabolic state of the organ or tissue under examination. Preparative methods, biodistribution data, and time function MR images are further provided.
摘要:
The invention relates to a method for the targeting of a therapeutic agent to a specific population of cells, wherein a complex is formed between the therapeutic agent and a polysaccharide capable of interacting with a cell receptor, and wherein the resulting complex is internalized into the cell by receptor mediated endocytosis (RME). In one embodiment of the invention, a complex of a therapeutic agent containing iron and the polysaccharide arabinogalactan may be formed and used to deliver iron specifically to hepatocytes by RME.
摘要:
An improvement is provided to a method for obtaining an in vivo MR image of an organ or tissue of an animal or human subject, of the type including administering to the subject as a contrast agent to enhance such MR image an effective amount of a colloid including superparamagnetic metal oxide particles dispersed in a physiologically acceptable carrier. In accordance with the improvement, the method includes preparing the colloid in a manner that provides a reduction in toxicity in comparison with that associated with administration of the colloid after terminal sterilization. The improvement may include sterilizing the colloid by filtration. In an additional embodiment, the colloid may be sterilized by filtration and preserved by lyophilization. The colloid may be lyophilized in the presence of a compatible excipient. The excipient utilized may include a dextran or a citrate anion. Other embodiments include related compositions and methods.
摘要:
This invention relates to compositions comprising a colloidal or particular metal oxide which are stabilized by low molecular weight carbohydrates. The carbohydrates are characterized by the fact that a) they are not retained on the surface of the metal oxide based on the equilibrium room temperature dialysis of about 2 ml of the metal oxide composition at 0.2 M metal concentration against deionized water; and b) they impart sufficient stability to the metal oxide compositions such that the compositions can withstand heat stress without perceptible aggregation as determined by a prescribed test procedure.